Typically, during execution of an instruction stream, an instruction is executed, a plurality of tests are performed, and then a next instruction is executed, etc. Certain instructions, however, require special handling. For instance, an execute instruction specifies a target instruction that can be modified prior to execution. This modification is to be managed. Further, an instruction that is crossing a memory boundary (e.g., a page boundary) requires that physically discontiguous portions of the instruction be obtained. Again, this situation is to be managed.
The handling of these circumstances is important. However, the handling of these circumstances during mainline processing degrades system performance.